Lars-Erik Tergenius

On the solid solution of copper in β-rhombohedral boron☆

Abstract In solid solutions of copper in β-boron, the copper atoms may occupy a maximum of four non-equivalent crystallographic positions. X-ray powder methods have been used for determining the manner in which these positions are filled when the copper content is increased.

Crystal structure of magnesium heptaboride Mg2B14

Abstract The crystal structure of a magnesium heptaboride, whose structural formula is Mg2B14, was determined from X-ray powder patterns according to a profile refinement technique and on the basis of isotypism with MgAlB14. The symmetry is orthorhombic and the lattice parameters are a = 5.970 A , b = 8.125 A and c = 10.480 A . The refinement is based on the space group Imam. The unit cell contains five non-equivalent boron and two nonequivalent magnesium atoms. The structure consists of chains of B12 icosahedra extending in the direction of the c axis. The chains are linked laterally via inter-icosahedral bonds or BB bonds involving nonicosahedral atoms, thus forming a three-dimensional boron network. The magnesium atoms occupy two types of holes in this network, corresponding to coordination numbers 12 and 16.

X-ray powder profile refinement of zirconium in β-rhombohedral boron

A Rietveld-type full-profile refinement technique, as adapted to Guinier--Haegg strictly K..cap alpha../sub 1/ monochromatized x-ray powder--film data (G. Malmros and J.O. Thomas, J. Appl. Crystallogr. 10, 7--11 (1977)), has been used to refine the structure of a solid solution of zirconium in ..beta..-rhombohedral boron with composition ZrB/sub approx. 51/. The space group is R anti 3m (No. 166) with hexagonal cell dimensions a = 10.9564(5), c = 24.0201(13) A, V = 2497.1 A/sup 3/ and with 309.4 boron atoms per unit cell. The R value roughly comparable to the R/sub f/ value of single-crystal work is 0.063. Zirconium atoms partially occupy two non-equivalent holes in the ..beta..-boron structure (28% at an 18(h) and 18% at a 6(c) position). 2 figures; 3 tables.

Room temperature synthesis and structural characterization of monoclinic LiCuO2 by X-ray and neutron diffraction

LiCuO2 was synthesized at room temperature by delithiation of Li2CuO2 using bromine in acetonitrile. The product shows broad diffraction lines which were analysed by the Rietveld refinement technique on X-ray and neutron powder data. The phase conforms to the NaCuO2 structure type

Refinement of the crystal structure of orthorhombic Mn2B (formerly denoted Mn4B)

Abstract The crystal structure of Mn4B was refined using single-crystal X-ray diffractometer techniques. The refinement of a crystal, representing a manganese-rich composition, gave a metal: B atomic ratio insignificantly different from 2:1. The space group adopted was Fddd and the lattice parameters obtained from powder diffraction were a = 14.539 5(8) A , b = 7.2914(11) A and c = 4.2082(3) A . The final index of agreement, R(F2), was 2.9%.

Single-crystal X-ray diffraction study of AlB31 of the β-rhombohedral boron structure

Abstract The structure of a crystal with the composition AlB 31 , prepared by arc-melting crystals of α-AlB 12 , has been investigated by single-crystal X-ray diffractometry. The space group is R 3 m (No. 166) with the hexagonal cell dimensions a = 10.965(1) A and c = 23.868(2) A. The structure was refined by a fullmatrix least-squares program to an R ( R w ) value of 0.034(0.040). The three-dimensional boron framework of the crystal is essentially equivalent to that of β-rhombohedral boron. The aluminum atoms partially occupy A 1 and D holes in the boron framework, and in the D hole the aluminum atoms are distributed over five positions. A disordered structure around the single B(15) atom site is discussed in connection with the Al distribution in the D hole.

The crystal structure of Pd2B

Abstract The crystal structure of Pd 2 B has been investigated by X-ray powder diffraction and single-crystal diffractometry. There are strong indications that Pd 2 B crystallizes with the anti-CaCl 2 type structure (C 35), space group Pnnm (No. 58), a = 4.6918(4) A, b = 5.1271(4) A, and c = 3.1096(3) A, but the extent to which the boron atoms assume ordered positions cannot be determined precisely with X-ray diffraction methods alone.

Microhardness measurements and phase analytical studies in the MnB system

Abstract The microhardness and cell dimensions of intermediate phases in the Mn-B system have been measured. The cell dimensions of the ternary phase Mn5SiB2 have also been determined. Boron dissolves interstitially in α-manganese. MnB2 has a very narrow range of homogeneity and transforms to Mn3B4 and MnB4 below about 1100 °C.

The crystal structure of Ta5B6

Abstract The structure of the new boride Ta5B6 has been determined and refined using single-crystal X-ray diffraction techniques. The structure is described in the space group Cmmm with a = 22.602(8) A , b = 3.1385(7) A and c = 3.2895(4) A . The refinement is based on 408 non-equivalent reflections and the final, conventional R value for these reflections is 2.34%. The structure is of the V5B6 type. The present structure refinement is the first single-crystal study of a phase crystallizing in the V5B6-type structure.

The crystal structure of Rh5B4

Abstract The crystal structure of Rh5B4 was investigated by X-ray powder diffraction and single-crystal diffractometry. Rh5B4 crystallizes in a hexagonal structure, with space group P63/mmc (no. 194), a = 3.3058(2) A , c = 20.394(4) A , c/a = 6.169, U = 193.01 A 3 and Z = 2. The structure is built up of close-packed layers of rhodium atoms with boron atoms accommodated in octahedral holes between the layers.